in the example below how possible is to rotate the nurbspath on its own z axis?
Not sure I entirely understand you issue. Assuming this is what you want to do.

In Object Mode select your curve and place the 3D cursor at its origin with the Shift+S menu.

Enter Edit Mode and select one or all of the vertex at the end of the curve. 

Change transform pivot to the 3D cursor with . Period key.

You can then rotate the selected vertex. For a smooth transformation like below try using Proportional Edit.